Syrian authorities have told Kofi Annan they have begun withdrawing troops from three areas, despite fresh reports this morning that they are attacking a suburb of the capital Damascus.

Ahmad Fawzi said that troops had begun withdrawing from Dera'a, Idlib and Zabadani, adding that UN member states were being asked to provide troops to a ceasefire monitoring mission, to be deployed in Syria after April 10.

An advance team sent by Annan was due to arrive in Damascus on Thursday to begin discussing their deployment, which requires a UN Security Council resolution.

"Yes they have told us that they have begun withdrawing troops from certain areas," Mr Fawzi told a news briefing in Geneva. "They have specified 3 cities – Dera'a, Idlib and Zabadani."

The Britain-based Syrian Observatory for Human Rights says "a major operation" is under way in the Damascus suburb of Douma, with tanks shelling the area and clashes between troops and army defectors.

Explosions and heavy machinegun fire rocked Douma, eight miles from the capital, sending columns of smoke rising from several buildings, anti-Assad activists from the Revolutionary Council of the Damascus Countryside said.

Fighting shows no sign of abating even though President Bashar al-Assad agreed more than a week ago to a six-point peace plan drawn up by UN-Arab League envoy Kofi Annan to end the year-long conflict.

Mr Fawzi said in Geneva on Thursday that countries were being asked to supply troops for the proposed UN monitoring mission to Syria. Mr Fawzi added that Mr Annan will travel to Tehran on April 11 for talks with senior Iranian officials on Syria.

Mr Annan's spokesman said he expects a ceasfire between Syrian troops and opposition forces to be in place no later than April 12.

On his visit to Syria, Norwegian Army former Chief of Staff Major-General Robert Mood, 54, was to examine prospects for UN observers to assess whether troops and insurgents respect the truce due to take effect by next Thursday.

Maj Gen Mood has experience of armed UN peacekeeping operations in Kosovo where around 60,000 troops were deployed in 1999 after a ceasefire and army withdrawal agreement were already in place.

Mr Annan's plan calls for Syrian troops to pull back from towns and cities ahead of a ceasefire with rebels under an "effective United Nations supervision mechanism". An "inclusive, Syrian-led political process" would follow.

Russia has said the withdrawal is under way, but Western leaders have voiced deep scepticism about Assad's good faith.

The opposition, British-based Syrian Observatory for Human Rights said army reinforcements were heading for Douma, rather than pulling back. Civilian casualties were reported there.

In northern Aleppo province, near the Turkish border, the Observatory said security forces were attacking two villages and had been fighting rebels for more than two hours.

"The loudspeakers at local mosques called for members of the regime army to defect and come into the towns," the group said, citing information from its network of activists inside Syria.

Four soldiers were killed and some civilians wounded. A sniper killed a rebel in Khan Sheikhoun in Idlib province.

Assad has been struggling to suppress what began as peaceful uprising in March 2011, but which has turned into an armed revolt as rebels fight back against troops and security forces.

The violence has prompted more than 40,000 Syrians to flee the country, including up to 900 who arrived in Turkey in the past 24 hours, a Turkish official said on Thursday. That was about double the average influx of recent days.

"There has been an increased flow through Reyhanli and the number was 800 to 900 yesterday," the official said.

Assad's government issued its latest official death toll for the 12-month uprising. It told the United Nations that 6,044 people had been killed, of whom 2,566 were soldiers and police.

The United Nations itself says Assad's forces have killed more than 9,000 people in the past year.

Syria's opposition and its Western and Arab supporters strongly doubt that Assad will withdraw his forces.

"The Syrian authorities have said they will do that by April 10," British Foreign Secretary William Hague said on Wednesday.

"There is no sign of them doing it so far. Attacks on the citizens, the civilians of their country have continued, the murder, oppression, and torture of the regime has continued ..."

But Russian Deputy Foreign Minister Gennady Gatilov said: "The Syrian side has begun withdrawing forces from cities. The main thing now is for all sides to carry out Annan's proposals."

Despite its pro-Assad tone, some diplomats have said Moscow has grown increasingly frustrated with Damascus and its failure to end the uprising but has denounced Western, Arab and Turkish calls for the Syrian leader to step aside.

"Russia believes regime change in Syria would result in an Islamist regime after a great deal of bloodshed," one senior diplomat told Reuters.